Multi-fuel burner



Dec. 31, 1963 F. J. cEELY 3,115,851

MULTI-FUEL BURNER Filed May 11, 1960 4 Sheets-Sheet 2 l Inventor v F/@Eofe/ck Z 655A? Attorney Dec. 31, 1963 F. J. cEELY MULTI-FUEL BURNER 4 Sheets-Sheet 3 Filed May 11, 1960 ttorney Dec. 31, 1963 F. J. cEELY MULTI-FUEL BURNER 4 Sheets-Sheet 4 Filed May 11, 1960 United States Patent fce lllgl Patented Dec. 3l, i933 3,llll5,351 MULTl-FUEL BURNER Frederick E. Ceely, Coiiege Point, NDY., assigner to Foster Wheeler Corporation, New York, NX., a corporation of New York Filed May ll, i960, Ser. No. 255,419 d Claims. (Cl. itil-22) This invention relates to fuel burners and' more particularly to an improved multi-fuel burner capable of burning a plurality of fuels, such as gas, oil and pulverized coal, which may be fired separately and/or i combination as `desired or `as determined by the amount of the particular fuel available.

ln multi-fuel burners of the Spud type wherein a plurality of elongated, circumferentially spaced, gas burner tubes )are arranged around a pulverized coal burner assembly, the burner unit is relatively large and cumbersome. ln addition, such burners fail to provide optimum combustion of the gas as weil as stable ignition due Ito the incomplete and non-uniform mixing of the gas and combustion air. ln an attempt to provide a Spud type burner capable of more eflicient combustion of gas, it has been proposed to position a supplemental air impeller member adjacent the gas burner tips. However, such construction has increased the complexity of the burner structure, particularly with respect to the provision for burning pulverized coal.

A further disadvantage of the heretofore known spud type multi-fuel burners is the flow of combustion gases from the furnace chamber into the gas manifold through the gas burner tubes and the gas burner tube supporting sleeves upon the shut down of the burner, and the attendant danger to an yoperator upon removal of one or more of the gas tubes for inspection and/for repair.

Accordingly, it is an object of the present invention to provide an improved multi-fuel burner of Athe ispud type of la more compact construction than heretofore known multi-fuel burners and wherein optimum combustion of all the fuels is achieved.

Another object of the invention is la multi-fuel burner havin-g a gas fuel burner assembly which provides eilicient and stable operation over a wide range of secondary air and fuel pressure 'and under sudden liuctuations of secondary air and/ or fuel flow. A further object of this invention is to provide a ispud type multi-fuel burner wherein optimum combustion of gas fuel is achieved without the need for supplemental combustion air control means, such as impeilers, in addition to the main secondary air register assembly.

A still further object of the present invention is to provide a spud type multi-fuel burner wherein the gas burner tubes may be readily disconnected and removed and replaced without danger to an openator.

More specifically the instant invention contemplates an improved multi-fuel burner which comprises a pulverized coal burner assembly disposed with the nozzle thereof extending through a windbox and terminating adjacent the outside of a burner port in the wall of a furnace chamber. A plurality of elongated gas burner tubes are arranged in circumferen-tial spaced relationship to each other and 'are disposed to extend through the central portion of the pulverized coal burner nozzle. Each of the gas burner tubes is connected at one end to a gas manifold and terminates at the `opposite end adjacent the outlet end of the coal burner nozzle. Each of the gas burner tubes is supported in a sleeve which extends from a point inwardly spaced from the gas burner tube tips to and through the involute section of the pulverized coal burner assembly. An oil burner assembly is disposed and suitably supported to extend through the involute section of the pulverized coal burner section and coaxia-lly through the coal burner nozzle. The oil burner assembly termina-tes adjacent the outlet end of the coal burner nozzle and is provided with a suitable fuel atomizing nozzle at the end thereof. This novel arrangement of various fuel burning means effects a conservation of space without detriment to .the efcient function of the pulverized coal burner assembly and results in a multi-fuel burner charaoterized by its simplicity and compractness.

The invention further provides a novel arrangement of the gas burner nozzles disposed at the tips of the gas burner tubes whereby optimum combustion of the gas is achieved. The gas burner nozzles are disposed Xat equidistant points along the periphery of an imaginary circular plane which extends parallel to the plane of the burner port. Each of the gas bur-ner nozzles are so constructed and arranged so as to direct a stream of gas extending from the nozzle toward the next adjacent gas burner nozzle at an angle of about 601 to 90 from the radius of the imaginary circular plane and outwardly of the latter toward the burner port. The stream of gas from each burner is directed toward the burner port so as to pass immediately adjacent the peripheral surface of the burner port. The gas nozzles are constructed and arnanged to direct the streams of gas with respect to the center of the imaginary circular plane in the same direction which direction is the same las the direction of rotation imparted to the secondary air by the air register. While improved results lare achieved with gas burner nozzles constructed and arranged to direct gas streams between about 60 to of the radius of the imaginary circular plane, it has been found that optimum gas combustion and stable fuel turning is achieved with the gas` streams directed toward the next adjacent nozzle at an angle of 66 from the nadius of the imaginary circular plane and `outwardly toward the burner port. With gas burner nozzles arranged to emit gstreams extending toward the next adjacent nozzie at an angle between 60 and less than 90 and outwardly tofward the burner port, the gas llow pattern is one of convergence and divergence (in the nature of an hour glass configuration), with maximum convergence Aoccurring before the streams of gas enter .the burner port. The aforedescribcd novel gas burner nozzle arrangement provides for improved gas combustion and llame stability without the need for supplemental `air control moans or appanatus.

The multi-fuel burner according to this invention is also provided with means for flowing air under pressure through the gas burner tube supporting sleeves to prevent combustion gas flow from the furnace chamber, through the burner port, .and into the supporting sieeves when the burner is shut down and a gas burner tube is to be removed for inspection or repair. ln addition, each gas burner tube is provided at its connection with the gas manifold with a check valve which allows flow of gas from the manifold into the gas burner tubes, but prevents flow of combustion gas from Athe furnace chamber, through the burner pont, into and through the gas burner -tubes to the manifold when the burner is taken out of service.

The invention will be more fully understood from the following description thereof when considered in connection with the accompanying drawings in which:

FIG. 1 is a view in cross-:section taken substantially along line l-l of FIG. 2 of the multi-fuel burner according to this invention;

FIG. 2 is `an end View in elevation fof the multi-fuel burner shown in FIG. 1;

FIG. 3 is a partial sectional view taken along line 3--3 of FlG. 1, somewhat enlarged;

HG. 4 is an end view in elevation of the gas fuel discharge end of the multi-fuel burner, somewhat enlarged;

FIG. 5 is an enlarged fragmentary view, partly in section, showing the means for supplying gas to the gas burner tubes and the means for supplying air to the sleeve air sealing chamber;

FIG. 6 is a fragmentary View on an enlarged scale showing the distal end of one of the sleeves;

FIG. 7 is a transverse section taken along line 7 7 of FG. 6;

FlG. 8 is a fragmentary view showing the orifices for admitting air from the air sealing chamber into the gas burner tube supporting sleeves;

FIG. 9 is an enlarged fragmentary View, in section, of the means for connecting the gas burner tubes to the manifold and the check valve disposed therein for controiling ow of fluid between the tube and manifold;

FiG. 10 is a plan View of the check Valve seal plate; and

FIG. ll is a sectional View taken substantially along line l-ll of FIG. 9;

FlG. 12 is a diagrammatic View showing the gas burner nozzle arrangement according to this invention.

Referring now to the drawings, and more particularly to FIGS. l, 2 and 3, the reference numeral il@ designates the novel multi-fuel burner, according to this invention, which is suitably supported by a Wall lil which Wall extends in spaced parallel relationship with a furnace Wall l2 of a furnace chamber. Wall 1l defines With wall 12 a windbox or plenum chamber 13 which is connected to receive combustion air from a suitable source thereof (not shown) to supply combustion air to a burner port or throat i4 in furnace wall 12.

The multi-fuel burner lt) comprises a pulverized fuel burner 15 which has a volute section i6 and a slightly tapered burner nozzle 17. Burner nozzle 17 is connected at one end to volute section le by means of a plurality of bolts i8 which extend through flanges provided on the volute section i6 and burner nozzle 17. The pulverized fuel burner 15 is disposed with the burner nozzle 17 extending through an opening 19 in Wall 11 toward the burner port 14 with the longitudinal axis of the nozzle in coextensive relationship to the longitudinal axis of burner port M. The pulverized fuel burner 15 is supported in opening 19 by a ring 2b having at one end an annular flange 21. Ring 2i) is secured, as by Welding, at one end to Wall il, adjacent the periphery of opening 19 and to pulverized fuel burner i5 by means of above mentioned bolts 18 which pass through annular flange 21. Burner nozzle 17 is dimensioned so that the discharge end thereof is disposed in close spaced relationship with burner port i4. The distal or discharge end portion of burner 17 is supported by an air register assembly 22.

Air register assembly 22 is of any suitable design as is Well known to those skilled in the art and, for illustration purposes, is shown as comprising a wall 25 having a plurality of radially extending fingers 26 and a ring member 27 spaced from wall 2S to define therebetween an annular, peripheral inlet opening 28 communicating with an outlet opening 29 dened by ring member 27. A plurality of vanes or doors 3i? (only two of which are shown in FIG. l) are pivotally supported circumferentially Within said inlet opening 2? between the distal ends of fingers 26 of wall 25 and ring member 2'7. The assembly is supported by Wall 12 With outlet opening 29 disposed in coaxial relation to burner port M by means of a plurality of brackets 31 which extend from Wall 25. Brackets 31 are suitably secured to a cylindrical bathe 32 which is secured, as by Welding, to wall i2 to project normal to Wall 12 in super-imposed spaced relationship to inlet opening 2S. Wall 25 is provided with an axial opening 33 to receive burner nozzle 17 of the pulverized fuel burner to support the latter.

Disposed Within the volute section 16 and burner nozzle 17 is a frusto-conical shaped baile or tubular member 34 which extends in coaxial relationship to the axis of burner nozzle 17. Baffie or tubular member 34 has a taper corresponding to the taper of burner nozzle 17 and is of smaller cross-sectional dimensions so that an annular pulverized fuel passageway 35 is defined between the outer surface of baffle or tubular member 34 and the inner surface of burner nozzle i7. The outer end of baiiie or tubular member 34 is provided with an annular outwardly extending flange 36 which is secured between side wall 37 and the flange of end Wall 33 of volute section 16 by means of bolts 39.

A cup shaped member lit) is secured, by means of bolts 23 (FIG. 2), to the exterior surface of end wall 37 of volute section 16 to form With end Wall 37 an air Seal-ing chamber 4i. The function and purpose of chamber 4l will be described fully hereinafter.

An annular or ring shaped gas manifold 42, having a diameter somewhat larger than the diameter of volute section 16 is secured to the cup shaped member 40 by means of a plurality of bolts 43 which pass through holes in radial lugs 44 extending inwardly from the inner circumference of manifold i2 (see FIG. 2). Gas manifold 112, as shown in FIGS. 2 and 5, is provided with an inlet connection 42A to which is connected a pipe (not shown) for delivery of a gaseous fuel under pressure to the manifold.

To provide for conducting the gaseous fuel from manifold 42 to the burner port 14, a plurality of elongated gas burner tubes 45 are disposed in circumferential spaced relationship to each other within baffle or tubular member 3d. Each of the elongated burner tubes 4,5 is shown as provided at the outer end with an integral U shaped end portion t6 While a fuel nozzle 6i) is disposed at opposite end of the burner tube. Each of the gas burner tubes i5 is supported and dimensioned to extend from manifold 42 through baille or tubular member 34 with nozzles dil of each gas burner tube lying slightly beyond the discharge outlet end of pulverized fuel burner nozzle 17. The baliie or tubular member 34, as shown, is an unbroken member providing a continuous surface around the gas burner tubes. By continuous, it is meant free of apertures or perforations for the passage of air, so that there is no way for air or pulverized fuel to ow within the baffle or tubular member and directly around the burner tubes. The novel disposition and arrangement of nozzles 60 will be hereinafter described in full.

An enlarged mounting head 47 is secured in a suitable manner, as by Welding or threading, to the end of U shaped end portion 46 of each gas burner tube Each mounting head 47 is provided with a bore 47A which communicates with the interior of the gas burner tube to which it is secured. Manifold 42 is provided in its outer Wall with a plurality of circumferentially spaced openings 42B (corresponding in number to the number of gas burner tubes 45, see FIGS. 1, 5 and 9). Each mounting head 47 is secured by means of bolts 4d (FiG. 2) to manifold 42 over an opening 42B in manifold 42 to cornmunicate the interior of the manifold with the interior of the gas burner tubes through bore 47A in the mounting head e7. To provide a fluid-tight seal between the face of mounting head 47 and manifold 6.2, a gasket 49 of the 0 ring type is provided in the face of each of the mounting heads (see FIG. 9). Each of the mounting heads is also provided with a check valve 59.

As best shown in FIGS. 9, l0 and ll, each check valve comprises a circular plate 51which is disposed across the flow area of bore 47A of mounting head 47 and is seated against an annular shoulder 52 spaced slifhtly inwardly of the face of the mounting head. Plate 5l is secured to shoulder 52 by tack Welding or in any other suitable manner. Plate Si, as best shown in FlG. 1l, is provided with two sets of concentrically arranged segmental slots or orifices 53 for passage of gas from the manifold into the bore of mounting head 47. A pin 55' is secured at one end td the center of plate 5l and extends normal to the surface thereof. A sealing disc 54 is slidably mounted on pin 55 for movement relative to plate Sli. Pin 5S is provided at its distal end with an enlarged head 55A which serves as a stop to limit the movement of disc 54 away hot combustion gas flowing from the furnace chamber through sleeves 6i and/or lgas burner tubes @i5 of the multi-fuel burner which is shut down. When one or more gas burner tubes d5 is to be removed for inspection and/or repair, valves e9 are opened to allow flow of air under pressure to flow through pipes ed into air sealing chamber fili, The air from sealing chamber 41 iiows into the passageways 66, between each gas burner tube d and the sleeve 6l in which it is supported, through openings 67 in sleeves 61 (HG. 8). This flow of air into passageways 65 removes any combustion gas which may have accumulated therein and prevents further combustion gas from iiowing into sleeve `dit. `Flow of combustion gas, through gas burner tubes 45', into manifold is prevented by check valves Sti. With the flow of gaseous fuel into manifold 42, shut-off, the combustion gas which may dow into the gas burner tubes acts against discs 54 of check valves 5? causing the discs to move against plates 5l. With the discs Sd against plates Si, as shown by the broken lline in HG. 9, orices 53 are seated closed to prevent iow of combustion gas into manifold 42,. Thus, when the mounting bolts i3 are removed from an enlarged mounting head 47 of a gas burner tube d5 preparatory to the lattcrs removal, combustion gas will not flow `from the manifold through opening 42B. The gas burner tube which has been disconnected from manifold 42 may now be withdrawn through its supporting sleeve 6i. With the flow of air through sleeve 6i from sealing chamber 4i, combustion gas is prevented from iiowing out of the open end of sleeve 6l, 4at pipe cap 67A, when the gas burner tube is fully Withdrawn.

From the foregoing description, it can be readily seen that an improved multi-fuel burner has been provided which is relatively simple and compact in construction, yand which provides for efficient combustion of gaseous fuel in conjunction with or separately from the combustion of pulverized fuel and/ or liquid fuel. The multi-fuel burner in addition, may be taken out of service without shut down of other burners, and gas burner tubes removed for inspection and/or repair without danger to the operating personnel from hot combustion gas flow through the gas burner tubes and their supporting sleeves.

Although, but one embodiment of the invention has been illustrated and described in detail, it is -to be understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts without departing from the scope and spirit of the invention, as the same will now be understood by those skilled in the art.

What is claimed is:

1. A multi-fuel burner `for providing combustion fuel to a furnace chamber having a wall and a burner port therein comprising, an air register means for the flow of combustion air into the furnace, said air register means having an air inlet opening, ian outlet opening, and means to impart to the combustion air a rotating helical flow through said outlet opening; a pulverized fuel burner having a tubular nozzle section including a first end adapted to receive a stream of pulverized fuel and yair and a discharge end disposed substantially concentricaily within said outlet opening of said air register means and in axial alignment therewith; a gas manifold disposed exteriorly of said pulverized fuel burner and connected to a source of gas under pressure; a plurality of circumferentiaily spaced elongated gas burner tubes connected at one end to said manifold and extending into and through said nozzle section of the puiverized fuel burner in spaced relationship to the inner surface of said nozzle section and terminating rat the opposite end thereof adjacent to the discharge end of the nozzle section, each of said gas burner tubes having a gas nozzle disposed at said opposite end for the discharge of gas; bale means disposed around said tubes in spaced relation with said nozzle section to provide with said nozzle section an annular ioV CTI

passageway for said pulverized fuei and air, said nozzles being arranged approximately at the periphery of an imaginary circular plane transverse to said nozzle section and disposed obliquely with respect to said plane to direct streams of gas in outwardly diverging paths from said outlet opening towards the next adjacent air nozzle at an angle between about 63 and labout 90 with a radius of said circular plane, said nozzles further being dispose to discharge gas in substantially the same direction as the direction of rotation of said combustion air.

2. ln a furnace assembly having :a furnace chamber, a wall, and a lburner port therein, a burner assembly for providing combustion fuel to the furnace chamber comprising, an air register for the ilow of combustion air into the furnace including an air inlet opening and an outlet opening the latter adjacent the burner port; an array of circumferentially spaced elongated gas burner tubes extending into said air register in spaced relation thereto having nozzle means disposed adjacent said outlet opening for the discharge of gas, said nozzle means being arranged approximateiy at the periphery of an imaginary circular plane transverse to said outlet opening; said burner assembly comprising means, including an unbroken tubular member coaxial with the array of gas burner tubes providing a continuous surface extending into said air register in spaced relation thereto and encompassing said Aburner tubes, means arranged to provide `an annular whirling motion to the combustion air flowing through said outlet opening and around said tubular member, said tubular member at one end thereof being disposed sufficiently close to the nozzle means to provide a quiescent area adjacent said nozzle means; said nozzle means being disposed obliquely with respect to said circular plane to direct streams of gas towards the next adjacent gas nozzle and to a point adjacent the inner periphery of said burner port, said gas streams further being directed at an angle between about 60 and about 90 with respect to a radius of said plane and in the general direction of rotation of the combustion air. j

3. In a furnace assembly having a furnace chamber, a wall, and a burner port therein, a multi-fuel burner for providing combustion fuel to the furnace chamber comprising, an air register means in communication with said burner port through which combustion air flows, said air register means having an air inlet opening, an outlet opening, and means to impart to the combustion air an annular rotating helical ow pattern through said burner port; a pulverized fuel burner having `a tubular nozzle section extending into said air register means including a rst end adapted to receive a stream of pulverized fuel and air and a discharge end disposed substantially concentricaliy within said outlet opening of said air register means and in axial alignment with the axis of said burner por-t; a gas manifold disposed exteriorly of said pulverized fuel `burner and connected to a source of gas under pressure; a plurality of circumferentially spaced elongated gas burner tubes connected at one end to said manifold and extendin" into and through said nozzle section of the pulverized fuel burner in spaced relationship to the inner surface of said nozzle section and terminating at the opposite end thereof adjacent to the discharge end of the nozzle section but spaced from either burner port; and baffle means disposed around said tubes in spaced relation with said nozzle section to provide with said nozzle section 1an annular passageway for said pulvcrized fuel and air, each of said gas burner tubes having a gas nozzle disposed at said opposite end for the discharge of gas, said nozzles being arranged approximately at the periphery of an imaginary circular plane transverse to the axis of said pulverized fuel burner nozzle and disposed obliquely with respect to said plane to direct streams of gas towards the next adjacent gas nozzle and to a point adjacent the inner periphery of sai burner port, said nozzles further being disposed to direct said streams of gas at an angle between about 60 and about 90 with respect to a radius of said circular pl-ane and in substantially the same direction as the direction of rotation of the combustion air through said burner port.

4. A multi-fuel burner according to claim 3 and including check-valve means in said gas burner tubes -for preventing the flow of combustion gases from the furnace chamber into said gas manifold when the gas burner tubes are not in service.

5. A multi-fuel burner `according to claim 4 and including elongated sleeves supporting said gas burner tubes and means for supplying air under pressure to the interior of said sleeves greater than the combustion gas pressure in said yfurnace to prevent the ow of combustion gases from the furnace when said tubes are removed from said sleeves.

6. In a furnace assembly having a furnace chamber, a wall, and a burner port therein, a multi-fuel burner for providing combustion fuel to the furnace chamber comprising, an air register means in communication with said burner port through which combustion -air flows, said air register means having an `air inlet opening, an outlet opening, and means to impart to the combustion air an annular rotating helical flow pattern through said burner port; a pulverized `fuel burner having a tubular nozzle section extending into said air register means including a rst end adapted to receive a stream of pulverized fuel and air and a discharge end disposed substantially concentrically within said ou-tlet opening of said a-ir register means and in axial alignment with the axis of said burner port; a gas manifold disposed ex-teriorly of said pulverized fuel burner and connected to a source of gas under pressure; a plurality of circumferentially spaced elongated gas burner tubes connected at one end to said manifold and extending into and through said nozzle section of the pulverized fuel burner in spaced relationship to the inner surface of said nozzle section and terminating at the opposite end thereof adjacent to the discharge end of the nozzle section but spaced from said burner port, each of said gas burner tubes having a gas nozzle disposed at s-aid opposite end for the discharge of gas, said nozzles being arranged approximately at the periphery of an imaginary circular plane transverse to the -axis of said pulverized fuel burner nozzle and disposed obliquely with respect to said plane-to `direct a stream of gas tow-ards the next adjacent gas nozzle rand to a point adjacent the inner periphery of said burner port, said nozzles fur-ther being disposed to direct said streams of gas at an angle between about and about 90 with respect -to a radius of said circular plane land in substantially the same direction as the direction of rotation of the combustion air through said burner port, and bafe means disposed annularly about said gas burner tubes and within said burner nozzle and concentric therewith arranged to separate said burner tubes from the ow of pulverized fuel and air in said burner nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 2,364,489 Taylor Dec. 5, 1944 2,806,518 Poole et al Sept. 17, 1957 2,823,628 Poole et al. Feb. 18, 1958 2,826,249 Poole Mar. 11, 1958 2,847,063 Reed et al. Aug. l2, 1958 2,921,542 Kidwell et al. Jan. 19, 1960 2,931,430 Marshall Apr. 5, 1960 FOREIGN PATENTS 931,249 France Oct. 6, 1947 UNITED STATES PATENT OFFICE CERTIFICATE 0F CCRRECTION Patent No. 3,115,851 December 3lq 1963 Frederick J., Ceely It is hereby certified that error appears n the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 27, for "gears" read bears column 8, line for "air" read gas line 2 for "either" read said signed and sealed this 2nd day o'f June 1964 (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A MULTI-FUEL BURNER FOR PROVIDING COMBUSTION FUEL TO A FURNACE CHAMBER HAVING A WALL AND A BURNER PORT THEREIN COMPRISING, AN AIR REGISTER MEANS FOR THE FLOW OF COMBUSTION AIR INTO THE FURNACE, SAID AIR REGISTER MEANS HAVING AN AIR INLET OPENING, AN OUTLET OPENING, AND MEANS TO IMPART TO THE COMBUSTION AIR A ROTATING HELICAL FLOW THROUGH SAID OUTLET OPENING; A PULVERIZED FUEL BURNER HAVING A TUBULAR NOZZLE SECTION INCLUDING A FIRST END ADAPTED TO RECEIVE A STREAM OF PULVERIZED FUEL AND AIR AND A DISCHARGE END DISPOSED SUBSTANTIALLY CONCENTRICALLY WITHIN SAID OUTLET OPENING OF SAID AIR REGISTER MEANS AND IN AXIAL ALIGNMENT THEREWITH; A GAS MANIFOLD DISPOSED EXTERIORLY OF SAID PULVERIZED FUEL BURNER AND CONNECTED TO A SOURCE OF GAS UNDER PRESSURE; A PLURALITY OF CIRCUMFERENTIALLY SPACED ELONGATED GAS BURNER TUBES CONNECTED AT ONE END TO SAID MANIFOLD AND EXTENDING INTO AND THROUGH SAID NOZZLE SECTION OF THE PULVERIZED FUEL BURNER IN SPACED RELATIONSHIP TO THE INNER SURFACE OF SAID NOZZLE SECTION AND TERMINATING AT THE OPPOSITE END THEREOF ADJACENT TO THE DISCHARGE END OF THE NOZZLE SECTION, EACH OF SAID GAS BURNER TUBES HAVING A GAS NOZZLE DISPOSED AT SAID OPPOSITE END FOR THE DISCHARGE OF GAS; BAFFLE MEANS DISPOSED AROUND SAID TUBES IN SPACED RELATION WITH SAID NOZZLE SECTION TO PROVIDE WITH SAID NOZZLE SECTION AN ANNULAR PASSAGEWAY FOR SAID PULVERIZED FUEL AND AIR, SAID NOZZLES BEING ARRANGED APPROXIMATELY AT THE PERIPHERY OF AN IMAGINARY CIRCULAR PLANE TRANSVERSE TO SAID NOZZLE SECTION AND DISPOSED OBLIQUELY WITH RESPECT TO SAID PLANE TO DIRECT STREAMS OF GAS IN OUTWARDLY DIVERGING PATHS FROM SAID OUTLET OPENING TOWARDS THE NEXT ADJACENT AIR NOZZLE AT AN ANGLE BETWEEN ABOUT 60* AND ABOUT 90* WITH A RADIUS OF SAID CIRCULAR PLANE, SAID NOZZLES FURTHER BEING DISPOSED TO DISCHARGE GAS IN SUBSTANTIALLY THE SAME DIRECTION AS THE DIRECTION OF ROTATION OF SAID COMBUSTION AIR. 